Virginiamycin and sodium monensin supplementation for beef cattle on pasture / Suplementação com virginiamicina e monensina sódica para bovinos de corte a pasto

The aim of this paper was to evaluate the effects of including virginiamycin (VM), sodium monensin (MON) or the association (VM+MON) in the energetic mineral supplement, on the intake and performance of beef cattle on pasture. Forty Nellore heifers with 24 months of age and initial body weight (BW) of 251.5±16.6kg, were distributed in four treatments in a randomized block design. Treatments consisted of adding VM, MON or VM+MON to the supplement (CONT). Additive concentrations were defined to reach a dose of 40 to 45mg/100kg BW. The herbage allowance was not a limiting factor for the animals' intake. Supplement intake was lower than expected, with 33.0, 18.8 and 26.3mg per 100kg BW for VM, MON and VM+MON, respectively. Dry matter intake (DMI, mean=2.65% BW) and animal performance were not affected by the inclusion of additives. The average daily gain (ADG) was 0.561kg/animal day-1. The inclusion of additives in energetic mineral supplement does not affect the DMI and the ADG of grazing animals. The variability in supplement intake and daily dose intake of additives may have influenced the performance of the animals. Monensin inclusion presented the less expensive supplementation cost, due to reduction in supplement intake without changing weight gain.(AU)

Objetivou-se avaliar o efeito da inclusão dos aditivos virginiamicina (VM), monensina sódica (MON) e associação (VM+MON) no suplemento energético-mineral sobre o consumo e desempenho de bovinos manejados em pastagem de Urochloa Brizantha cv. Marandu. Foram utilizadas 40 novilhas Nelore com 24 meses de idade e peso corporal (PC) inicial médio de 251,5+16,6kg distribuídas em delineamento em blocos ao acaso com quatro tratamentos. Os tratamentos consistiam de suplemento energético-mineral (CONT) acrescido de VM, MON ou VM+MON. A oferta de forragem não limitou o consumo dos animais. O consumo dos aditivos foi de 0; 33,0; 18,8 e 26,3mg por 100kg de PC para CONT, VM, MON e VM+MON, respectivamente. O consumo de matéria seca e o desempenho dos animais não foram afetados pela inclusão dos aditivos. O ganho médio diário dos animais foi de 0,561kg dia -1 , sem diferença entre os tratamentos. A inclusão de aditivos no suplemento energético-mineral não alterou o CMS e o desempenho dos animais em pastejo. A variabilidade no consumo de suplemento e na dose ingerida dos aditivos pode ter influenciado o desempenho dos animais.(AU)

Does virginiamycin supplementation affect the metabolism and performance of Nellore bulls grazing under low and high gain rates?

This study aimed to evaluate the effect of virginiamycin on the metabolism and performance of growing Nellore bulls under low and high gain rates on pasture. In experiment 1, 80 Nellore bulls (age = 12 ± 2 months, body weight = 258 ± 15 kg) were assigned to 16 paddocks in a 2 × 2 randomized block factorial arrangement. In experiment 2, 12 cannulated Nellore bulls were assigned to three 4 × 4 balanced Latin squares. The factors were: (1) mineral salt without or with virginiamycin, and (2) low or high gain rate. No interaction was noted between factors (p > .10). Animals fed virginiamycin had greater average daily gain (14%, p < .01), body weight (11 kg, p = .05), plasma nonesterified fatty acid (20%, p < .01), serum calcium concentration (2.62%, p = .04), and total protozoa (p = .03) and had the same bacterial proportion (p > .27). Animals with a low gain rate had greater serum urea concentration (19.6%, p < .01) and ruminal ammonia nitrogen (62%, p < .01). Thus, virginiamycin increases the performance and changes the metabolism of growing Nellore bulls under low and high gain rates on pasture.

Effect of Dietary Fructooligosaccharide (FOS) Supplementation on Ileal Microbiota in Broiler Chickens.

The dietary effect of fructooligosaccharide (FOS) supplementation as an alternative to antibiotics on ileal mucosa and digesta microbiota was investigated in broiler chickens (n = 180). The study included three dietary treatments from d1 to 21: 1) positive control (PC), a wheat-corn-soybean meal based diet containing antibiotics (virginiamycin and monensin); 2) negative control (NC), as wheat-corn-soybean meal based diet without antibiotics; and 3) NC + FOS, as NC diet supplemented 0.5% of FOS. Ileal mucosa and digesta were collected and subjected to 16S rRNA-based next generation sequencing. No significant difference on α-, ß-diversity and bacterial phyla was observed between ileal mucosa and digesta or between the three dietary treatments. Partial least square discriminant analysis and Venn analysis showed that different bacterial genera were associated with different ileal sites or diets. A distinct distance on ileal mucosa bacteria communities were observed between PC and NC + FOS dietary treatments. FOS supplementation increased the number of unique genera and resulted in a more diverse microbiota in the ileal mucosa when compared with PC and NC groups. Furthermore, microorganisms that have pathogenic properties such as Helicobacter and Desulfovibrio were found significantly reduced when compared between NC and NC + FOS groups in the ileal mucosa. Lachnospiraceae (f) was greater in the ileal mucosa than that in the digesta, particularly among the NC + FOS dietary group. Overall, supplementing FOS in broiler chicken diets may be able to modulate gut microbiota in favor of chicken health, which in turn, can be used as an alternative method to replace antibiotic growth promoters (AGPs). Future investigation on the mechanism of FOS and other prebiotic products as dietary supplements is warranted.

Evaluation of Aloe vera and synbiotic as antibiotic growth promoter substitutions on performance, gut morphology, immune responses and blood constitutes of broiler chickens.

This study was performed to investigate the effect of dietary supplementation with Aloe vera (AV) powder and synbiotic as growth promoter agents on performance, gut morphology, immune responses, hematology and serum biochemistry in broilers. A total of 240-day-old male broiler chicks (Ross 308) were randomly assigned to six treatments with four replicates. Birds were offered either a corn-soybean meal basal diet (control) or the basal diet supplemented with 200 mg/kg virginiamycin (VM), 1 g/kg synbiotic (Syn), 2.5 g/kg AV (AV1), 5.0 g/kg AV (AV2) or 7.5 g/kg AV (AV3). Chickens fed any of the diets, except diet AV1, exhibited better feed conversion ratios at the 14-28 day period and higher average daily gain and duodenal villus height/crypt depth ratio at 42 days than those fed the control diet. Synbiotic supplementation caused a marked increase in the serum antibody titer against infectious bursal disease and infectious bronchitis vaccines. Feeding diet AV3 significantly increased red blood cell count and hemoglobin concentration, and decreased serum triglyceride level compared to the control group. The results suggested that dietary inclusion of 5 and 7.5 g/kg AV, similar with synbiotic supplementation, can be applied as effective alternatives to in-feed antibiotics for broiler diets.

Influence of protein nutrition and virginiamycin supplementation on feedlot growth performance and digestive function of calf-fed Holstein steers.

Two experiments were conducted to examine the influence of protein and virginiamycin (VM) supplementation on feedlot growth performance, digestion, and metabolizable AA (MAA) supply of calf-fed Holstein steers. Growth performance and dietary energetics were evaluated in 120 Holstein steers (127 ± 9 kg). During the initial 112-d feeding period, a steam-flaked corn-based diet was balanced to meet either 100% (MAB) or 87% (UREA) of MAA requirements. Diets were supplemented with or without 22.5 mg/kg VM in a 2 × 2 factorial arrangement. Subsequently (d 112 to 308), all steers received the UREA diet with or without VM. During the initial 112-d, MAB increased ADG, G:F, and dietary NE ( < 0.01). Thereafter, when all steers received the UREA diet, ADG, G:F, and dietary NE were not different ( > 0.10) across initial supplementation treatments. Overall (d 1 to 308), MAB did not affect ADG ( > 0.10) but enhanced G:F efficiency ( = 0.03) and dietary NE ( = 0.05). During the initial 112-d period and through the remainder of the experiment, VM increased G:F ( < 0.01) and dietary NE ( < 0.01). Four Holstein steers (146 ± 4 kg) with cannulas in the rumen and proximal duodenum were used in a 4 × 4 Latin square design to evaluate initial 112-d treatment effects on digestive function. There were no treatment effects ( > 0.10) on ruminal digestion of OM, NDF, starch, microbial efficiency, or total tract digestion of OM and NDF. The MAB increased indispensable AA flow to the small intestine ( < 0.01) and total tract digestion of N ( < 0.01) and starch ( = 0.04). Observed AA supply to small intestine was in agreement with expected supply ( = 0.96). Virginiamycin decreased ( = 0.04) nonammonia N flow to the small intestine and did not affect ( > 0.10) total tract N digestion. Extrapolating from AA supplies in the metabolism study, MAB satisfied indispensable AA requirements during the initial 112-d period, whereas the UREA diet met 73.5% and 79.2% of methionine and lysine requirements, respectively. During the subsequent periods (d 112 to 308) indispensable AA supplies exceeded theoretical requirements. We conclude that enhancements in energy utilization when diets are balanced to meet MAA requirements of calf-fed Holstein steers during the initial 112-d feedlot period remain appreciable throughout time on feed. Virginiamycin enhanced efficiency of energy utilization throughout the feedlot growing-finishing period.

Effect of plant extracts derived from thyme on male broiler performance.

The effect of dietary thyme-oil extract (TOE) supplementation on immune functions of broilers were assessed by feeding graded levels (50, 100, 200, or 400 ppm) of TOE to male broiler chicks during a 42-d feeding trial compared with negative- or positive-control diets. Dietary control treatments included a negative-control diet with no feed-additive supplementation and 2 positive-control groups supplemented with either virginiamycin or zinc bacitracin. In total, 300 1-day-old Ross × Ross male broilers were randomly assigned to 6 dietary treatments that consisted of 5 replicates of 10 birds each. On d 21 and 42, 2 birds from each replicate were killed by cervical cutting to measure the relative weights of spleen and bursa of Fabricius. At 25 d of age, chicks were injected with 0.5 mL of 10% SRBC suspension. Broilers fed with 200 ppm of TOE had heavier weights of bursa of Fabricius than those fed other dietary treatments at d 42 of age. Furthermore, dietary inclusion of 100 ppm of TOE resulted in higher (P < 0.05) total immunoglobulin response in primary antibody titer against sheep erythrocytes compared with other dietary treatments. On the other hand, diet modifications had no significant effect on blood leukocyte subpopulations and heterophil-to-lymphocyte ratio. These results suggest that dietary supplementation with TOE, especially at the level of 100 ppm, can improve immunological responses of broiler chicks.

Effects of dietary pyrroloquinoline quinone disodium on growth performance, carcass yield and antioxidant status of broiler chicks.

Pyrroloquinoline quinone (PQQ), a putative essential nutrient and redox modulator in microorganisms, cell and animal models, has been recognized as a growth promoter in rodents. Growth performance, carcass yield and antioxidant status were evaluated on broiler chickens fed different levels of PQQ disodium (PQQ.Na2). A total of 784 day-old male Arbor Acres (AA) broilers were randomly allotted into seven dietary groups: negative control group (NC) fed a basal diet without virginiamycin (VIR) or PQQ.Na2; a positive control group (PC) fed a diet with 15 mg of VIR/kg diet; and PQQ.Na2 groups fed with 0.05, 0.10, 0.20, 0.40 or 0.80 mg PQQ.Na2/kg diet. Each treatment contained eight replicates with 14 birds each. The feeding trial lasted for 6 weeks. The results showed that chicks fed 0.2 mg PQQ.Na2/kg diet significantly improved growth performance comparable to those in PC group, and the feed efficiency enhancement effects of dietary PQQ.Na2 was more apparent in grower phase. Dietary addition of PQQ.Na2 had the potential to stimulate immune organs development, and low level dietary addition (<0.1 mg/kg) increased plasma lysozyme level. Broilers fed 0.2 mg PQQ.Na2/kg diet gained more carcasses at day 42, and had lower lipid peroxide malondialdehyde content and higher total antioxidant power in plasma. The results indicated that dietary PQQ.Na2 (0.2 mg/kg diet) had the potential to act as a growth promoter comparable to antibiotic in broiler chicks.

Synergy of streptogramin antibiotics occurs independently of their effects on translation.

Streptogramin antibiotics are divided into types A and B, which in combination can act synergistically. We compared the molecular interactions of the streptogramin combinations Synercid (type A, dalfopristin; type B, quinupristin) and NXL 103 (type A, flopristin; type B, linopristin) with the Escherichia coli 70S ribosome by X-ray crystallography. We further analyzed the activity of the streptogramin components individually and in combination. The streptogramin A and B components in Synercid and NXL 103 exhibit synergistic antimicrobial activity against certain pathogenic bacteria. However, in transcription-coupled translation assays, only combinations that include dalfopristin, the streptogramin A component of Synercid, show synergy. Notably, the diethylaminoethylsulfonyl group in dalfopristin reduces its activity but is the basis for synergy in transcription-coupled translation assays before its rapid hydrolysis from the depsipeptide core. Replacement of the diethylaminoethylsulfonyl group in dalfopristin by a nonhydrolyzable group may therefore be beneficial for synergy. The absence of general streptogramin synergy in transcription-coupled translation assays suggests that the synergistic antimicrobial activity of streptogramins can occur independently of the effects of streptogramin on translation.

Effects of mannan oligosaccharide and virginiamycin on the cecal microbial community and intestinal morphology of chickens raised under suboptimal conditions.

There is an increasing movement against use of antibiotic growth promoters in animal feed. Prebiotic supplementation is a potential alternative to enhance the host's natural defense through modulation of gut microbiota. In the present study, the effect of mannan oligosaccharide (MOS) and virginiamycin (VIRG) on cecal microbial ecology and intestinal morphology of broiler chickens raised under suboptimal conditions was evaluated. MOS and VIRG induced different bacterial community structures, as revealed by denaturing gradient gel electrophoresis of 16S rDNA. The antibiotic treatment reduced cecal microbial diversity while the community equitability increased. A higher bacterial diversity was observed in the cecum of MOS-supplemented birds. Quantitative polymerase chain reaction results indicated that MOS changed the cecal microbiota in favor of the Firmicutes population but not the Bacteroidetes population. No difference was observed in total bacterial counts among treatments. MOS promoted the growth of Lactobacillus spp. and Bifidobacterium spp. in the cecum and increased villus height and goblet cell numbers in the ileum and jejunum. These results provide a deeper insight into the microbial ecological changes after supplementation of MOS prebiotic in poultry diets.

Supplementation of direct-fed microbials as an alternative to antibiotic on growth performance, immune response, cecal microbial population, and ileal morphology of broiler chickens.

An experiment was conducted to investigate the supplementation of direct-fed microbials (DFM) as an alternative to antibiotics on growth performance, immune response, cecal microbial population, and ileal morphology of broiler chickens. A total of 800 one-day-old male broiler chicks (Ross × Ross) were randomly allotted to 4 dietary treatments with 4 replicate pens per treatment (50 birds/replicate pen). The 4 dietary treatments fed for 35 d were a corn-soybean meal basal diet (control); control plus 0.1% virginiamycin, as an antibiotic growth promoter (AGP); control plus 0.1% direct-fed microbials that contained Lactobacillus reuteri (DFM 1); and control plus 0.1% direct-fed microbials that contained a mixture of L. reuteri, Bacillus subtilis, and Saccharomyces cerevisiae (DFM 2). Results showed that dietary AGP and DFM supplementation significantly increased (P < 0.05) the BW gain of broilers during 0 to 21 d. The feed intake was reduced, whereas the feed conversion was improved significantly when birds were fed DFM 2 at 0 to 7 d of age. The white blood cell and monocyte levels were significantly higher in the DFM 2 group compared with the control. In addition, feeding DFM significantly (P < 0.05) increased the plasma immunoglobulin levels where a higher level was observed in DFM 2 compared with those of the other treatments. Neither DFM nor AGP treatments affected the cecal Lactobacillus and Salmonella content; however, cecal Escherichia coli content significantly decreased in broiler chickens fed DFM and AGP. The ileal villus height, and width and total thickness of muscularis externa were significantly increased when birds were fed DFM compared with AGP and control. These results indicate that the dietary supplementation of DFM increases the growth performance of birds at an early age, stimulates the immune response, decreases the number of E. coli, and improves the ileal morphology of broiler chickens. Thus, DFM that contained a mixture of several beneficial microorganisms could be a viable alternative to antibiotics in the broiler diets.

The characterization of lactic acid producing bacteria from the rumen of dairy cattle grazing on improved pasture supplemented with wheat and barley grain.

AIMS: To identify and characterize the major lactic acid bacteria in the rumen of dairy cattle grazing improved pasture of rye grass and white clover and receiving a maize silage and grain supplement with and without virginiamycin. METHODS AND RESULTS: Eighty-five bacterial isolates were obtained from the rumen of 16 Holstein-Friesian dairy cows. The isolates were initially grouped on the basis of their Gram morphology and by restriction fragment length polymorphism analysis of the PCR amplified 16S rDNA. A more definitive analysis was undertaken by comparing the 16S rDNA sequences. Many of the isolates were closely related to other previously characterized rumen bacteria, including Streptococcus bovis, Lactobacillus vitulinus, Butyrivibrio fibrisolvens, Prevotella bryantii and Selenomonas ruminantium. The in vitro production of L- and/or D-lactate was seen with all but five of the isolates examined, many of which were also resistant to virginiamycin. CONCLUSION: Supplementation of grain with virginiamycin may reduce the risk of acidosis but does not prevent its occurrence in dairy cattle grazing improved pasture. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows that lactic acid production is caused, not only by various thoroughly researched types of bacteria, but also by others previously identified in the rumen but not further characterized.

Virginiamycin improves phosphorus digestibility and utilization by growing-finishing pigs fed a phosphorus-deficient, corn-soybean meal diet.

Evaluations of the nutritional effect of antibiotics have largely centered on effects related to the digestibility and utilization of protein and energy. The current study evaluated the potential effect of virginiamycin (VIR) on P digestibility in swine. A total of 70 barrows (mean initial BW = 51 to 64 kg) were used in 4 nutrient-balance experiments. A basal, corn-soybean meal diet that was not supplemented with any inorganic source of P was used in each experiment. In Exp. 1, two diets were tested: basal vs. basal plus 11 mg/kg of VIR. In Exp. 2, four diets were used with a 2 x 2 factorial arrangement of 0 and 11 mg/kg of VIR and 0 and 750 phytase (PHY) units/kg of diet (PU/kg). Experiments 3 and 4 were the same as Exp. 2, except PHY was reduced to 300 PU/kg. For all experiments, VIR improved P digestibility (32.71 to 37.72%, P < 0.001) and Ca digestibility (54.99 to 58.30%, P = 0.002). The addition of PHY improved both P and Ca digestibility (P < 0.001); 750 PU/kg increased P digestibility 27.3% (from 34.6 to 61.9%, P < 0.001), whereas 300 PU increased it 13.8% (from 33.4 to 47.2%, P < 0.001). In an experiment conducted to evaluate the long-term effects of VIR on gut microbial profile, pigs (24 gilts and 8 barrows; mean BW = 29.1 +/- 0.50 kg) were fed a simple corn-soybean meal diet for 16 wk with a 2 x 2 factorial arrangement of VIR (0 and 11 mg/kg) addition and 0.15% dicalcium phosphate deletion. The long-term feeding of VIR in both the control diet and the diet with a marginally reduced P level resulted in a change in ileal microbial profile. A positive numerical increment in the number of phytate-utilizing bacteria was observed in both the normal and P-deleted diets (log unit increments of 12.4 and 17.2% over the respective controls, P = 0.13) when VIR was added. The addition of VIR also tended to affect lactobacilli populations (main effect, P = 0.11; interaction, P = 0.02); VIR decreased lactobacilli in the normal-P diet but did not affect this bacterial population in the P-deleted diet. In conclusion, the antibiotic VIR improves both Ca and P digestibility in pigs. The increase in digestibility is not as great as that provided by PHY, but because the potential mechanism of action (altered microbial populations) differs from that of PHY (direct addition of an enzyme), there can be a degree of additivity in P digestibility improvement when both products are used.

[Therapeutic perspectives of linezolid in the management of infections due to multiresistant Gram-positive pathogens]. / Le prospettive terapeutiche di linezolid nelle infezioni da patogeni Gram-positivi multiresistenti.

Multi-antibiotic resistant Gram-positive cocci represent emerging pathogens especially in the setting of the immunocompromised, hospitalized patients, in particular when surgery, invasive procedures, or prosthetic implants are of concern, patients are admitted in intensive care units, or underlying chronic disorders and immunodeficiency are of concern, and broad-spectrum antibiotics and/or immunosuppressive drugs are widely administered. The spectrum of available antimicrobial compounds for an effective management of these relevant infections is significantly impaired in selection and clinical efficacy by the emerging and spread of methicillin-resistant and more recently glycopeptide-resistant Gram-positive microbial strains linezolid, together with the recently licensed quinupristin-dalfopristin, daptomycin and tigecycline, followed by a number of glycopeptides, fluoroquinolones, and other experimental compounds represent an effective response to these concerns, due to their innovative mechanisms of action, their maintained or enhanced activity against multiresistant pathogens, their effective pharmacokinetic/pharmacodynamic properties, their frequent possibility of synergistic activity with other compounds effective against Gram-positive pathogens, and a diffuse potential for a safe and easy administration, also when compromised patients are of concern. The main problems related to the epidemiological and clinical features of multiresistant Gram-positive infection, the potential clinical indications of all recently available compounds compared with the standard of treatment of resistant Gram-positive infections, and updated data on efficacy and tolerability of linezolid have to be clarified.

Characterization of intestinal microbiota and response to dietary virginiamycin supplementation in the broiler chicken.

The inclusion of antibiotic growth promoters, such as virginiamycin, at subtherapeutic levels in poultry feeds has a positive effect on health and growth characteristics, possibly due to beneficial effects on the host gastrointestinal microbiota. To improve our understanding of the chicken gastrointestinal microbiota and the effect of virginiamycin on its composition, we characterized the bacteria found in five different gastrointestinal tract locations (duodenal loop, mid-jejunum, proximal ileum, ileocecal junction, and cecum) in 47-day-old chickens that were fed diets excluding or including virginiamycin throughout the production cycle. Ten libraries (five gastrointestinal tract locations from two groups of birds) of approximately 555-bp chaperonin 60 PCR products were prepared, and 10,932 cloned sequences were analyzed. A total of 370 distinct cpn60 sequences were identified, which ranged in frequency of recovery from 1 to 2,872. The small intestinal libraries were dominated by sequences from the Lactobacillales (90% of sequences), while the cecum libraries were more diverse and included members of the Clostridiales (68%), Lactobacillales (25%), and Bacteroidetes (6%). To assess the effects of virginiamycin on the gastrointestinal microbiota, 15 bacterial targets were enumerated using quantitative, real-time PCR. Virginiamycin was associated with increased abundance of many of the targets in the proximal gastrointestinal tract (duodenal loop to proximal ileum), with fewer targets affected in the distal regions (ileocecal junction and cecum). These findings provide improved profiling of the composition of the chicken intestinal microbiota and indicate that microbial responses to virginiamycin are most significant in the proximal small intestine.

Effect of butyric acid on the performance and carcass yield of broiler chickens.

Short-chain fatty acids such as butyrate are considered potential alternatives to antibiotic growth promoters. The efficacy of butyric acid on performance and carcass characteristics of broiler chickens was tested in two studies. The effect of dietary butyrate on the ability to withstand coccidial oocyte challenge also was investigated. In experiment 1, male broiler chickens were fed diets supplemented with 0 or 11 ppm virginiamycin or 0.2 or 0.4% butyric acid (as mono-, di-, and triglyceride). In experiment 2, broilers were fed bacitracin methylene disalicylate or 0.1 or 0.2% butyric acid. In another trial, birds vaccinated against coccidiosis were challenged with oocytes at 21 d and examined 6 d later. In experiment 1, diet treatments had no effect on body weight gain. Feed intake of the birds fed 0.4% butyric acid was decreased (P < 0.01) compared with birds fed the nonmedicated diet during the starter period, whereas birds fed 0.2% butyric acid had similar feed intake to the control birds. In experiment 2, diet treatments did not affect the performance of broiler chicks while carcass weight and breast meat yield increased (P < 0.01) in birds fed 0.2% butyric acid. With oocyte challenge, birds that had received butyric acid before challenge showed higher growth rate following the challenge compared with birds that received nonmedicated feed. Bacitracin decreased (P < 0.05%) duodenal villi crypt depth, whereas villus length was similar in birds fed butyric acid or the nonmedicated control diet. These results show that 0.2% butyric acid can help to maintain the performance and carcass quality of broilers, especially in vaccinated birds challenged with coccidiosis.

The effect of virginiamycin in diets with adequate or reduced dietary calcium or nonphytate phosphorus for broilers.

Four experiments (EXP) were conducted to evaluate the effects of virginiamycin (Vm) in diets adequate or reduced in Ca or nonphytate P (nPP) levels on growth performance and bone response variables in chicks. All diets were corn-soybean meal (C-SBM) based, and all treatments were replicated 6 or 8 times with 5 or 6 chicks each. In EXP 1 and 2, the dietary treatments were 1) C-SBM with 1.00% Ca and 0.45% nPP (positive control; PC); 2) C-SBM with 0.80% Ca and 0.45% nPP (0.80Ca); 3) C-SBM with 1.00% Ca and 0.35% nPP (0.35nPP); and 4 to 6) Diets 1 to 3 with 11 (EXP 1) or 22 (EXP 2) ppm of Vm. In EXP 1, daily gain (ADG), feed intake (ADFI), bone breaking strength (BBS), milligrams of ash per gram of Ca intake (ASH/Ca), and BBS per gram of Ca (BBS/Ca) or nPP (BBS/nPP) intake were increased in chicks fed Vm (P < 0.04 to 0.07). Chicks fed the 0.35nPP diet with Vm had increased ADG, ADFI, BBS, milligrams of tibia ash (ASH), BBS/Ca, and BBS/nPP (nPP x Vm, P < 0.03 to 0.10). Chicks fed the 0.80Ca diet with Vm had increased ASH, milligrams of ASH per gram of nPP intake (ASH/ nPP), and ASH/Ca (P < 0.01 to 0.09). Tibia ash, BBS, gain:feed (G:F), BBS/nPP, and ASH/nPP were decreased in chicks fed the 0.80Ca diet (P < 0.01 to 0.07). Bone ash percentage (BAP), BBS, BBS/Ca, ASH, and ASH/Ca were decreased in chicks fed the 0.35nPP diets (P < 0.01); ASH/ nPP was increased (P < 0.01). In EXP 2, BAP, ASH, ASH/ Ca, and ASH/nPP were increased in chicks fed Vm (P < 0.02 to 0.07). Chicks fed the 0.80Ca diet had a decreased ASH/nPP (P < 0.04) but an increased BBS/Ca and ASH/ Ca (P < 0.01 to 0.02). Chicks fed the 0.35nPP diet had decreased ADG, ADFI, G:F, BBS, BAP, ASH, ASH/Ca, and BBS/Ca (P < 0.01 to 0.04), but BBS/nPP and ASH/ nPP were increased (P < 0.01 to 0.04). In EXP 3, the dietary treatments were 1) PC; 2) C-SBM with 0.70% Ca and 0.45% nPP (0.70Ca); 3) C-SBM with 1.00% Ca and 0.25% nPP (0.25nPP); 4 to 6) Diets 1 to 3 with 9 ppm of Vm. The addition of Vm to the 0.25nPP diet decreased BBS (nPP x Vm, P < 0.06), but Vm increased BBS in the 0.70Ca and PC diets (P < 0.02). Chicks fed the 0.25nPP diet had decreased ADG, ADFI, and BBS (P < 0.01), and chicks fed the 0.70Ca diets had reduced ADFI, BBS, and G:F (P < 0.03 to 0.10). In EXP 4, 4 levels of nPP (0.15, 0.25, 0.35, or 0.45%) and 3 levels of Vm supplementation (0, 11, or 22 ppm) in a 4 x 3 factorial arrangement were used. The addition of Vm increased ADG, BBS, ASH, ASH/Ca, and ASH/nPP only in chicks fed diets with 0.35 or 0.45% nPP (nPP x Vm, P < 0.05). Daily gain, ADFI, G:F, BBS, BAP, BBS/Ca, and ASH were increased as nPP levels were increased (P < 0.01), but BBS/nPP and ASH/nPP were decreased (P < 0.01) as nPP levels were increased. The results obtained from these EXP indicate that Vm, regardless of supplementation level, can partially overcome an nPP deficiency when nPP levels are = 0.35%.

Effects of virginiamycin and a mannanoligosaccharide-virginiamycin shuttle program on the growth and performance of large white female turkeys.

Shuttle programs involving dietary supplementation of mannanoligosaccharides (MOS) and virginiamycin (VM) were evaluated in turkeys by their effects on growth performance, body weight uniformity, and carcass yield characteristics. Diets containing no growth promoter (control), VM (22 mg/kg), or a shuttle program (MOS-VM) of MOS (0 to 6 wk of age at 500 mg/ kg) and VM (6 to 14 wk of age at 22 mg/kg) were fed to Hybrid female turkeys. All diets were formulated to exceed NRC nutrient requirements. Each treatment was assigned to 8 replicate floor pens containing 20 birds that were reared from 1 to 98 d of age. Body weights and feed consumption were recorded at 3-wk intervals, and mortality and culled birds were recorded daily. At the conclusion of the trial, 2 birds per pen were randomly chosen for carcass yield analysis. Feeding VM alone significantly (P < 0.05) increased body weight compared with control fed birds during all periods. The MOS-VM shuttle program resulted in early growth depression for birds less than 3 wk of age, possibly influenced by an unplanned cold stress, but better growth than the nonmedicated control birds after 6 wk of age. Birds fed VM had superior (P < 0.05) feed conversion ratio from 0 to 3 wk, which persisted until 14 wk (P < 0.10). There were no treatment effects on overall feed consumption, uniformity, mortality, or cull rate. Processing yields or weight of various parts were also unaffected by treatment.

Role of quinupristin/dalfopristin in the treatment of Gram-positive nosocomial infections in haematological or oncological patients.

Gram-positive pathogens, primarily Staphylococcus aureus, coagulase-negative staphylococci, viridans group streptococci, and enterococci, are now the predominant causes of infection in neutropenic haematology/oncology patients, but are often resistant to multiple antibiotics. Glycopeptides have been the only alternative antibiotic treatments for multidrug-resistant Gram-positive infections to date. However, glycopeptides are not always effective or well tolerated, and can produce nephrotoxic or ototoxic effects. Quinupristin/dalfopristin is a recently introduced streptogramin antibiotic that is active in vitro against most of the major Gram-positive pathogens causing infection in neutropenic patients. Recent studies of the in vitro susceptibility of clinical isolates of Gram-positive pathogens to quinupristin/dalfopristin are summarized. Pre-clinical and clinical studies of the efficacy and safety of quinupristin/dalfopristin in the treatment of Gram-positive infections are reviewed. Quinupristin/dalfopristin is active in vitro against the vast majority of recent isolates of relevant Gram-positive pathogens, including methicillin-resistant staphylococci, viridans group streptococci, and vancomycin-resistant Enterococcus faecium, but excluding Enterococcus faecalis. Pre-clinical and clinical data indicate the efficacy of quinupristin/dalfopristin in infections caused by these organisms, including bacteraemia and catheter-related infections. Quinupristin/dalfopristin is not associated with nephrotoxicity or ototoxicity. Quinupristin/dalfopristin is a potential alternative to glycopeptides in haematology or oncology patients with multidrug-resistant Gram-positive infections, especially those who are unresponsive to, or intolerant of, glycopeptides.

Safety and efficacy of quinupristin/dalfopristin for treatment of invasive Gram-positive infections in pediatric patients.

BACKGROUND: Antibiotic-resistant Gram-positive pathogens are an increasingly common cause of serious pediatric infections. Although quinupristin/dalfopristin demonstrates favorable activity against resistant Gram-positive pathogens (including many vancomycin-resistant and methicillin-resistant staphylococci), published experience in the pediatric patient population is limited. METHODS: We retrospectively analyzed data from the global quinupristin/dalfopristin Emergency-Use Program, which enrolled patients with serious Gram-positive infections who had no further therapy options because of resistance to, failure on or intolerance to standard antibiotic treatments. Our subset included safety and efficacy data from pediatric patients (age <18 years). There were no restrictions on underlying diseases, severity of illness or prior/concomitant antimicrobial use. RESULTS: Between May 1995 and October 1999, 127 pediatric patients with 131 infections were enrolled. Microbiologic confirmation of etiology was available in 124 patients. All patients had 1 or more concomitant conditions, including malignancy and solid organ or bone marrow transplantation. The most frequent causative pathogens were vancomycin-resistant (80%), spp. (7%), methicillin-resistant (6%) and (4%). All but 21 patients received intravenous quinupristin/dalfopristin 7.5 mg/kg every 8 h. The favorable clinical response rate of quinupristin/dalfopristin was 86 of 124 (69%); the favorable microbiologic response rate was 97 of 124 (78%). Eleven patients (8%) had nonvenous adverse events classified as possibly or probably related to quinupristin/dalfopristin. CONCLUSIONS: Quinupristin/dalfopristin demonstrated favorable response rates and was reasonably well-tolerated in pediatric patients with serious Gram-positive infections unable to receive alternative therapy. In our opinion quinupristin/dalfopristin is a therapeutic option for the management of such infections.

Combination of quinupristin-dalfopristin and gentamicin against methicillin-resistant Staphylococcus aureus: experimental rabbit endocarditis study.

The combination of quinupristin-dalfopristin (Q-D) and gentamicin was tested against two strains of gentamicin- and dalfopristin-susceptible methicillin-resistant Staphylococcus aureus (MRSA). One strain was susceptible to macrolides, lincosamides, and streptogramin B type antibiotics (MLS(B)), and the other was constitutively resistant to these antibiotics by virtue of the ermA gene. The checkerboard method and time-kill curves showed that the combination of Q-D and gentamicin was indifferent. A rabbit endocarditis model simulated the pharmacokinetics achieved in humans receiving intravenous injections of Q-D (7.5 mg/kg of body weight three times a day) and gentamicin (3 mg/kg once daily). For the MLS(B)-susceptible strain, a 4-day regimen reduced mean bacterial titers (MBT) in vegetations from 8.5 +/- 0.8 log CFU/g (control group) to 4.1 +/- 2.6 (gentamicin), 3.0 +/- 0.9 (Q-D), and 2.6 +/- 0.5 log CFU/g (Q-D plus gentamicin). For the strain constitutively resistant to MLS(B), a 4-day regimen reduced MBT in vegetations from 8.7 +/- 0.9 log CFU/g (control group) to 5.0 +/- 2.2 (gentamicin), 5.2 +/- 2.2 (Q-D), and 5.1 +/- 2.4 log CFU/g (Q-D plus gentamicin). The differences between control and treatment groups were significant for both strains (P < 0.0001), although there was no significant difference between treatment groups. No resistant variant was isolated from vegetations, and no significant difference in MBT in vegetations of treatment groups after 1-day regimens was observed. This experimental study found no additive benefit in combining Q-D and gentamicin against dalfopristin- and gentamicin-susceptible MRSA.